The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Self-expanding stents are medical devices used to treat diseased areas of a variety of body lumens, including, but not limited to: veins, esophagi, bile ducts, colons, and ureters. Generally, self-expanding stents are inserted into a body lumen with a delivery system to help support a weak point in the body lumen or to bypass it completely. A self-expanding stent is a tubular structure with at least one lumen that runs through it. Self-expanding stents are often made of a wire or mesh material that can elastically contract and expand.
A self-expanding stent usually has two states: a delivery state and a deployed state. In the delivery state, the self-expanding stent is radially compressed to a smaller diameter to allow the self-expanding stent to be delivered through a body lumen to the diseased area. Once the self-expanding stent is positioned at the diseased area, the self-expanding stent is then radially expanded to a larger diameter into a deployed state. Once in the deployed state, the self-expanding stent is secured to the walls of the body lumen through friction or is attached to the wall of the body lumen using various methods. Depending on the application, the deployed self-expanding stent then maintains the structure of a weakened body lumen wall or creates a new fluid channel to bypass the diseased area.
Self-expanding stents are manufactured to naturally tend towards an expanded, deployed state. Prior to insertion into the body lumen, self-expanding stents are generally radially compressed to a delivery state, and will naturally expand back to a deployed state once the means used to compress the stent is removed. Often, the self-expanding stent is compressed using an outer sheath: a simple tubular structure with a lumen running through it. The self-expanding stent is placed within the lumen of the outer sheath, which radially compresses it into the delivery state. Once the self-expanding stent is in position within the body lumen, the outer sheath is removed from the stent and the stent expands into its deployed state.
While using an outer sheath to deliver a self-expanding stent is common, it has several disadvantages. For example, as the stent is compressed to a smaller diameter, a greater deployment force is required to remove the outer sheath from the stent and thus deploy the stent. If the force required to remove the outer sheath from the stent is too high, positioning difficulties as well as potential damage to the body lumen could occur. Therefore, the stent can only be compressed to a certain diameter when using an outer sheath. Additionally, self-expanding stents are typically expanded by pulling the outer sheath from the distal end of the stent to the proximal end, meaning the distal end of the stent expands first and the proximal end last. This limitation can lead to inaccurate placement of the stent. In addition, high frictional forces during withdrawal of the outer sheath may damage the stent. Therefore, it is desirable to provide a device that improves on these disadvantages.